3,695 research outputs found
Public Policy and Law Since Love Canal: Unintented and Unforseen Consequences of Love Canal and the Superfund Legislation
The Mandamus Power of the United States Courts of Appeals: A Complex and Confused Means of Appellate Control
Performance of sinking and nonsinking phytoplancton taxa in a gradient of mixing depths
According to a recent dynamical model, the depth of a well-mixed water column should have contrasting effects on the abundances of sinking and nonsinking phytoplankton taxa. Because of increasing light limitation, nonsinking taxa should decline monotonically with increasing mixing depth, and because of sinking loss limitation at low mixing depths, sinking taxa should peak at intermediate mixing depths. Along a gradient of mixing depths, the position of this maximum should increase with increasing taxon-specific sinking velocity and decrease with increasing background turbidity. In two field-enclosure experiments, we investigated the effects of mixing depth and background turbidity on a variety of sinking and nonsinking phytoplankton taxa. We exposed the natural, 100-µm screened phytoplankton community of a clear, unproductive, but silica-rich lake to a gradient of mixing depths (1.5- 15 m) during 4-6 weeks. To mimic two different background turbidities, the transparent enclosure walls were surrounded by either white or black foliage. Although diatoms suffered from high sedimentation losses at low mixing depths, they dominated biomass at all mixing depths throughout both experiments. Results were largely in accordance with model predictions. Specific gross growth rates of most common taxa were negatively related to mixing depth. In both experiments, the abundances of most sinking taxa showed a unimodal pattern along the mixing depth gradient, while two of three motile taxa declined monotonically with mixing depth. The depths where these taxa reached their maximal abundances were positively related to taxon-specific sinking velocity and negatively related to background turbidity
Band Gap and Edge Engineering via Ferroic Distortion and Anisotropic Strain: The Case of SrTiO
The effects of ferroic distortion and biaxial strain on the band gap and band
edges of SrTiO (STO) are calculated using density functional theory and
many-body perturbation theory. Anisotropic strains are shown to reduce the gap
by breaking degeneracies at the band edges. Ferroic distortions are shown to
widen the gap by allowing new band edge orbital mixings. Compressive biaxial
strains raise band edge energies, while tensile strains lower them. To reduce
the STO gap, one must lower the symmetry from cubic while suppressing ferroic
distortions. Our calculations indicate that for engineered orientation of the
growth direction along [111], the STO gap can be controllably and considerably
reduced at room temperature.Comment: 5 pages, 5 figures. To be published in Phys. Rev. Let
Hyperfine clock transitions of bismuth donors in silicon detected by spin-dependent recombination
Bismuth donors ion-implanted in 28Si and natSi are studied using magnetic resonance spectroscopy based on spin-dependent recombination. The hyperfine clock transition, at which the linewidth is significantly narrowed, is observed for the bismuth donors. The experimental results are modeled quantitatively by molecular orbital theory for a coupled pair consisting of a bismuth donor and a spin-dependent recombination readout center, including the effect of hyperfine and Zeeman interactions
Spectroscopic Discovery of the Broad-Lined Type Ic Supernova 2010bh Associated with the Low-Redshift GRB 100316D
We present the spectroscopic discovery of a broad-lined Type Ic supernova (SN
2010bh) associated with the nearby long-duration gamma-ray burst (GRB) 100316D.
At z = 0.0593, this is the third-nearest GRB-SN. Nightly optical spectra
obtained with the Magellan telescopes during the first week after explosion
reveal the gradual emergence of very broad spectral features superposed on a
blue continuum. The supernova features are typical of broad-lined SNe Ic and
are generally consistent with previous supernovae associated with low-redshift
GRBs. However, the inferred velocities of SN 2010bh at 21 days after explosion
are a factor of ~2 times larger than those of the prototypical SN 1998bw at
similar epochs, with v ~ 26,000 km/s, indicating a larger explosion energy or a
different ejecta structure. A near-infrared spectrum taken 13.8 days after
explosion shows no strong evidence for He I at 1.083 microns, implying that the
progenitor was largely stripped of its helium envelope. The host galaxy is of
low luminosity (M_R ~ -18.5 mag) and low metallicity (Z < 0.4 Z_solar), similar
to the hosts of other low-redshift GRB-SNe.Comment: 6 pages, 4 figures, 1 table, submitted to ApJ Letter
The resummation of inter-jet energy flow for gaps-between-jets processes at HERA
We calculate resummed perturbative predictions for gaps-between-jets
processes and compare to HERA data. Our calculation of this non-global
observable needs to include the effects of primary gluon emission (global
logarithms) and secondary gluon emission (non-global logarithms) to be correct
at the leading logarithm (LL) level. We include primary emission by calculating
anomalous dimension matrices for the geometry of the specific event definitions
and estimate the effect of non-global logarithms in the large limit. The
resulting predictions for energy flow observables are consistent with
experimental data.Comment: 31 pages, 4 figures, 2 table
Jet-veto in bottom-quark induced Higgs production at next-to-next-to-leading order
We present results for associated Higgs+n-jet production in bottom quark
annihilation, for n=0 and n>=1 at NNLO and NLO accuracy, respectively. We
consider both the cases with and without b-tagging. Numerical results are
presented for parameters relevant for experiments at the LHC.Comment: 27 pages, 13 figures, 8 table
The Lantern Vol. 8, No. 1, December 1939
• Christmas Resurrection • Autumn\u27s Song • Henry Cavendish • The Mystery of Loon Cove • All Hail, Fair Modesty • Mischall • Gift of the Magi • Camera-Phobia • One Envying a Poet • Sonnetshttps://digitalcommons.ursinus.edu/lantern/1019/thumbnail.jp
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